Contractible couplings or clamps are employed to annularly circumscribe a member to be clamped, such as a conduit, and the purpose of the coupling is to exert a force or pressure on the member being embraced which produces a uniform circumferential force for sealing purposes. While such couplings may employ bolts, worm drives or other contracting components, the couplings may consist of wire or bands formed of resilient material, such as spring steel, wherein the resiliency of the coupling material produces the contracting force for gripping and compressing the member embraced.
Conventional annular couplings or clamps utilizing the resiliency of the coupling material to produce contracting forces are not suitable for installations wherein relatively high temperatures are encountered, such as in exhaust systems for internal combustion engines, in that heating of the coupling material tends to adversely affect the ability of the coupling to maintain effective contraction forces.
It is an object of the invention to provide a contractible coupling or clamp of the resilient type wherein the coupling may be used with flared conduit joints or connections in relatively high temperature applications without being adversely affected by the temperature of the member being embraced.
Another object of the invention is to provide a radially contractible coupling of an annular configuration for use with flared conduit connections wherein contraction is produced by the resiliency of an annular band, and a plurality of fingers defined upon the band engage the conduit flared surfaces and permit circumferentially spaced engagement of the coupling upon the conduits.
A further object of the invention is to provide a contractible coupling utilizing the resiliency of a coupling band to produce the contraction forces wherein the coupling engages the member being embraced at predetermined spaced locations, and the coupling band is in radial spaced relationship to the embraced member.
Yet another object of the invention is to provide a method for forming a contractible coupling of stamped sheet metal having the aforementioned objects and advantages wherein the coupling may be economically fabricated and is of homogeneous one-piece construction.
In the practice of the invention a sheet metal blank, preferably of stainless steel, is formed wherein the blank includes a body of generally rectangular configuration having a longitudinal length, ends and lateral edges. A tab is formed at each end of the body extending from the body ends, and the tabs are located upon opposite sides of the body center line or axis. Each of the tabs includes a flange at an outer lateral tab edge which is later deformed inwardly to reinforce the tab against deflection under bending forces.
A plurality of fingers homogeneously extend from the body lateral edges in spaced relationship to each other. Each of the fingers includes a base portion at which the finger is connected to the body edge, a free end, and an intermediate portion between the base portion and the free end.
After the coupling blank has been stamped the fingers are bent 180.degree. at their base portion whereby the fingers will be located in spaced relationship to the body inner surface and will extend over the body inner surface. The length of the fingers is such that the free ends of the fingers extend "inwardly" a distance less than the center of the body as defined by the body lateral edges, and the portions of the fingers at the free ends are curved to form convex conduit engagable surfaces and the free ends extend toward the body inner surface without engaging the same. The fingers' intermediate portion is approximately parallel to the body inner surface.
The tab flanges are formed inwardly as the adjacent fingers are bent, and as the tab flanges are disposed at substantially 90.degree. to the plane of the tabs, the flanges will support the tabs against bending forces applied perpendicular to the plane of the tabs.
The coupling blank is now formed into an annular configuration wherein the inner diameter of the coupling is defined by the innermost surfaces of the fingers, i.e. the intermediate portion of the fingers. The length of the body is such that the tabs at each body end extend adjacent and "past" each other in a manner generally tangential to the coupling configuration, and the form of the tabs is such that squeezing of the tabs or forcing the tabs toward each other tends to increase the diameter of the annular configuration of the coupling.
After the sheet metal coupling is fully shaped, it is heat treated in order to retain the resiliency desired and resistance to deflection. The blank is formed of a spring steel material, preferably of a stainless steel composition.
The fingers extending from the lateral edges of the coupling body are in alignment with each other with respect to the body width, and accordingly, the aligned fingers, together, will form opposed pressure locations on the flares of the conduits being clamped.
The coupling is used by squeezing the tabs toward each other by an appropriate tool, such as a plier-like implement, and this squeezing of the tabs will open the diameter of the coupling and permit the coupling to be placed upon the flares of the conduits to be clamped. Release of the tabs permits the coupling to contract toward its normal diameter, which will be resisted as the fingers engage the flares of the conduits being embraced.
As only the inwardly curved portions of the free ends of the fingers will engage the flares of the conduits being clamped, a plurality of circumferentially spaced opposed clamping locations are produced on the conduit flares which are substantially evenly distributed throughout the circumference of the conduits. The curved portions of the finger's free ends will engage the flares of the connected conduits in opposed relationship and produce both radial and axial forces on the flares to produce an effective sealed relationship between the conduits at their flares, and the limited resilient nature of the fingers will aid in locating the coupling on the conduit's flares and equalize the forces of the fingers on the flares. As the fingers are radially spaced from the coupling body, the body is in spaced relationship to the conduits being clamped, and heat from the clamped member is not directly transferred to the coupling body. Further, as the coupling body is in spaced relationship to the conduits being clamped, air may circulate therebetween which aids in maintaining the coupling body at a lower temperature.
As the contractible coupling in accord with the invention is formed from a single sheet metal blank, the fabricating techniques are inexpensive and may be accomplished by high production techniques.